Canis ISSN: 2398-2942

Wound: vacuum-assisted closure

Synonym(s): VAC; sub-atmospheric closure

Contributor(s): Otto Lanz, Laura Owen

Introduction

  • VAC therapy is the controlled application of sub-atmospheric pressure (-125 mmHg) to a wound using a therapy unit to intermittently or continuously convey negative pressure to a specialized wound dressing to help promote wound healing.
  • VAC therapy is an alternative strategy in the management of a variety of wounds encountered in human medicine and surgery.
  • In human surgery VAC is used for decubital ulcers, degloving injuries, distal extremity wounds, as a means to secure split thickness skin grafts in anatomically challenging areas, post-sternotomy dehiscence following cardiac surgery, open peritonitis, abdominal wound dehiscence and perineal wounds.
  • In dogs, VAC has been described for use in the treatment of distal extremity shearing injuries and for stabilization of skin grafts. In cats, VAC has been described for promotion of granulation tissue and contraction of large skin/soft tissue defects.
  • Application of sub-atmospheric pressure causes the foam dressing to collapse and the resultant mechanical forces are transmitted to all wound surfaces in contact with the foam dressing. In response to applied forces, an increased rate of mitosis is induced, new vessels are formed, and adjacent tissues are recruited through viscoelastic flow.
  • Ilizarov bone distraction technique demonstrates how tissue moves and grows in response to the application of mechanical force, with viscoelastic flow increased mitotic rate, and distraction histiogenesis. Severalin vivoandin vitrostudies have proven that mechanical stress applied to cells increases the expression of certain growth factors (eg vascular endothelial growth factor and fibroblast growth factor-2) that are known stimulators of angiogenesis and cell proliferation. A recent study reviewed the use of sub-atmospheric pressure to treat wounds and proposed two broad mechanisms of action: removal of fluid and mechanical deformation. Fluid removal both decreases edema, thus decreasing interstitial pressure and shortening distances of diffusion, and removes soluble factors that may slow the healing process. The relationship of mechanical deformation to increased growth is well known to plastic surgeons, as it is the basis of tissue expansion.
  • Vacuum application results in continuous removal of the excess fluid from the interstitium at the wound periphery. This results in a decrease in the local interstitial pressure, thus restoring blood flow to those vessels previsouly compressed. Experimental studies found that VAC promoted capillary blood flow velocity, increased capillary bed and blood volume, stimulated endothelial proliferation and angiogenesis, narrowed endothelial spaces and restored the integrity of the capillary basement membrane. By increasing capillary bed and blood volume and by stimulating angiogenesis, VAC could improve blood circulation in wounds. By narrowing endothelial spaces and by restoring the integrity of capillary basement membranes, VAC could decrease the permeability of blood vessels and wound edema. However, another report found a relative hypoperfusion close to the wound edge. The hypoperfused zone was larger at high negative pressures and was especially prominent in subcutaneous tissue.
  • Bacterial colonization of the wound is reduced via improved blood flow and local tissue defences, as well as the continuous removal of exudate from the wound surface.
  • Minimizing movement of the area treated must be considered.
    Veterinarians should be aware that the vacuum-asssisted closure system is patented in most countries in EuroAsia and Americas.

Uses

Advantages

  • Early surgical debridement Wound: debridement remains the mainstay of early wound care. Vacuum-assisted closure (VAC) however, as an adjunctive procedure, offers significant advantages compared to conventional wound care methods.
  • VAC decreases the time to wound healing by increasing the deposition of granulation tissue:
    • Early wound closure.
    • Early skin grafting (with improved graft adherence).
    • Early hospital discharge.
  • In a retrospective study of shearing wounds in dogs treated using traditional dressings, a complete bed of granulation tissue was evident in 2.0 to 8.7 weeks (Beardsley & Schrader, 1995).
  • In a study evaluating 15 dogs with distal shear wounds treated using VAC, all cases showed a significant decrease in the amount of tissue edema surrounding the wound by 2-7 days after the initial application of the VAC, and granulation tissue was typically present within the first 48 hours of VAC application following 2-4 days of traditional wound care. The overall mean time until surgery with the VAC system was 4.6 days (range, 2-7 days). The results of that study indicated that VAC therapy is emerging as an acceptable adjunctive modality for wound care of the distal extremities of dogs.
  • Argentaet al, found that the VAC negative pressure technique is effective in accelerating granulation tissue formation and subsequent wound shrinkage, allowing fewer procedures or treatment options to be instituted to achieve wound closure.
  • The VAC provides a safe and effective adjunctive method for securing skin grafts and is associated with improved graft survival as measured by a reduction in the number of repeated skin graft attempts.
  • The use of negative-pressure dressing as skin graft reinforcement has a number of advantages:
    • Can be applied easily and quickly.
    • Conforms readily to any surface.
    • Removes fluid, thereby minimizing seroma or hematoma formation.
    • Immobilizes the graft tissue interface, reducing failures due to movement.
  • Discomfort to the patient is minimal.
  • Bandage changes can be done less frequently than with customary techniques, reducing stress/risks associated with sedation/anesthesia and enabling improved nutrition, with fewer days of forced starvation for dressing changes.
  • Infection potential is diminished.

Disadvantages

  • The most common complication is erosion of surrounding tissue due to pressure caused by the evacuation tubing.
  • Excessive in-growth of granulation tissue into the foam dressing, which predominantly occurs if dressing changes are performed at >48 hour intervals.
  • Removal of the foam, if left in place longer then the recommended 48 hours, can disrupt the newly formed capillary beds and can result in minor bleeding.
  • Desiccation of the tissue when an inadequate seal is obtained.
  • Dermatitis immediately adjacent to the wound can occur as a result of completely removing the adhesive at each bandage change.
    This problem can be prevented by removing the adhesive tape only around the open cell ether foam, while sparing the remaining of the adhesive tape attached to the body.
  • VAC therapy should not be used in cases with overt signs of infection, with significant necrotic tissue within the wound (debride first!), if active hemorrhage, or in neoplastic lesions.
  • Loss of vacuum if the adhesive seal is broken or if the drain tube is punctured.

Requirements

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Preparation

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Procedure

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Aftercare

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Outcomes

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Prognosis

  • Good.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Owen L J, Hotston-Moore A, Holt P E (2009) Vacuum-assisted wound closure following urine-induced skin and thigh muscle necrosis in a cat. Vet Comp Orthop & Traumatol 22 (5), 417-421 PubMed.
  • Ben-Amotz R, Lanz O I, Miller J M et al (2007) The use of vacuum-assisted closure therapy for the treatment of distal extremity wounds in 15 dogs. Vet Surg 36 (7), 684-690 PubMed.
  • Guille A E, Tseng L W, Orsher R J (2007) Use of vacuum-assisted closure for management of a large skin wound in a cat. JAVMA 230 (11), 1669-1673 PubMed.
  • Lambert K V, Hayes P, McCarthy M (2005) Vacuum Assisted Closure: A review of development and current applications. Eur J Vasc Endovasc Surg 29 (3), 219-226 PubMed.
  • Benson J A, Boudrieau R J (2002) Severe carpal and tarsal shearing injuries treated with an immediate arthrodesis in seven dogs. J Am Anim Hosp Assoc 38 (4), 370-380 PubMed.
  • Brière C (2002) Use of a reverse saphenous skin flap for the excision of a grade II mast cell tumor on the hind limb of a dog. Can Vet J 43 (8), 620-622 PubMed.
  • Argenta L C, Morykwas M J (1997) Vacuum assisted closure: a new method for wound control and treatment: clinical experience. Ann Plast Surg 38 (6), 563-576 PubMed.
  • Morykwas M J, Argenta L C, Shelton-Brown E I et al (1997) Vacuum-assisted closure: a new method for wound control and treatment: animal studies and basic foundation. Ann Plast Surg 38 (6), 553-562 PubMed.
  • Beardsley S L, Schrader S C (1995) Treatment of dogs with wounds of the limbs caused by shearing forces: 98 cases (1975-1993). JAVMA 207 (8), 1071-1075 PubMed.
  • Swaim S F (1985) Management and bandaging of soft tissue injuries of dog and cat feet. J Am Anim Hosp Assoc 21 (3), 329-340 VetMedResource.
  • Vig M M (1985) Management of integumentary wound of the extremities in dogs: an experimental study. J Am Anim Hosp Assoc 21 (2), 187-192 VetMedResource.

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